Drill rigs are commonly used in oil and gas production and well service operations to bore substantial distances below the earth's surface. A drill rig generally includes a drawworks for raising and lowering a drill string in a borehole. The drawworks generally includes a large drum or spool that holds the drill string. The drill string extends from the drum to a derrick that supports a block and tackle arrangement holding a travelling block. The travelling block provides a mechanical advantage for raising and lowering the drill string in the borehole. A clutch releasably connects a drive system to the drum to rotate the drum to reel in the drill string. To lower the drill string, the clutch may disengage the drive train from the drum, and a brake connected to the drum may be released to allow the weight of the drill string to rotate the drum to release drill string from the drum.
The size and weight of the drill rig, drawworks, and travelling block often approaches or exceeds one hundred tons, depending on the particular application. In particular applications, for example, the drill string alone may weigh several hundred tons, depending on the depth of the borehole and drilling equipment attached to the drill string. As a result, many drill rigs include a travelling block controller that applies operating limits to safely control the operation of the drawworks to reduce or eliminate catastrophic equipment damage or personal injury.
The drill rig is often located on a mobile platform to allow convenient relocation of the drill rig to a particular drill site. During relocation, the derrick and other large components associated with the drawworks may be collapsed, retracted, or disassembled to facilitate transportation on the mobile platform. Once the mobile platform is relocated, the components are then re-assembled to support the desired drilling operations.
While the mobile platform enhances portability of the drill rig to various locations, the enhanced portability also introduces additional dangers to an already dangerous operation. For example, the relocated mobile platform should be as level as possible to ensure even distribution of the extremely large forces placed on the derrick. In addition, the derrick and other large components associated with the drawworks must be properly re-assembled and fully operational to ensure safe operation of the drill rig. While additional procedures may be implemented to address these and other additional dangers, inadvertent errors or procedural omissions may increase the chance of a catastrophic failure. Therefore, the need exists for an improved drill rig and method for operating the drill rig that incorporates one or more interlocks to ensure safe and reliable operation of the drill rig.